1. Field of the Invention
The present invention relates to a refrigerant transportation hose (an air-conditioner hose) and specifically to a refrigerant transportation hose that is mounted in an engine compartment of an automobile.
2. Description of the Related Art
Generally, a rubber hose is used for a refrigerant transportation hose that is mounted in an engine compartment of an automobile in terms of assembility, a vibration transmission property, flexibility and the like. For example, proposed is a hose having a structure of a tubular inner rubber layer in which refrigerant is circulated, a reinforcing layer formed on an outer peripheral surface of the tubular inner rubber layer and an outer rubber layer formed on an outer peripheral surface of the reinforcing layer (for example, see Japanese Unexamined Patent Publication No. 07-068659).
Since such a refrigerant transportation hose requires resistance to gas permeation (gas barrier properties) for blocking or reducing gas permeation (permeation of refrigerant such as Freon gas (trade name) available from Du Pont de Nemours and Company) from the inside of the hose to the outside, butyl rubber excellent in gas barrier properties is used for such an inner rubber layer.
Recently, to further improve gas barrier properties, some trials has been conducted. For example, a white filler (talc) to be blended in the butyl rubber is increased or a plasticizer (oil) to be blendend therein is decreased.
However, since the increasing amount of a white filler (talc) or the decreasing amount of a plasticizer (oil) increases hardness of the inner rubber layer, the resulting hose is inferior in flexibility. Further, since viscosity of the material increases when manufacturing a hose, rubber scorching may occur due to increasing pressure of an extruder head and fluidity of rubber may deteriorate, resulting in a problem of inferior moldability. Further, since the hose itself becomes brittle, there are other problems such as deterioration of fatigue properties such as a bending fatigue property and a dumbbell fatigue property.